The P2 grip has been bio-mechanically tested by Quintic Consultancy Ltd. The results showed a correlation in the ability of golfers to strike putts closer to the Sweetspot.
The P2 is designed with two flat sides which fill out the palm of both hands. This prevents the hand being positioned any other way but squarely on the grip. As a result the hands are square to the putter face. You'll find your ability to keep the lead wrist square to your target much simpler, which is key for good putting.